w FOREST PRODUCTS LABORATORY (Madison 5, Wis.) FOREST SERVICE §\\ U. S. DEPARTMEHT OF AORICULTURE Approved Technical Article DEPOSITO RY | Chemical Utilization and Forest Management 1 EDWARD G. LOCKE Chief, Division of Derived Products, Forest Products Laboratory," Forest Service, U. S. Department of Agriculture Forest management plans must be intimately related to the way the crop is to be used. Diversified processes and plants must be developed before intensive forest management is possible or profitable. The relation between chemical utilization and forest management is discussed in some detail. IN any discussion of chemical utili- zation of wood, two facts should be kept in mind. One is that a forest will produce a great many products; it will produce sawlogs, veneer bolts, poles, [>iling, fence posts, pulpwood, and a arge amount of material that we now call "logging residue." The second fact is that utilization Eractices dictate how the forest will : managed. If a sawmill is the only outlet in the area, the forest will be managed to produce sawlogs; if a pulpmill is the only outlet, the land will be managed for pulpwood. Here in the Southeast you have seen a one-product farm economy in opera- tion. You know that to have stabilized agriculture farms must produce not oqe, but a number of products. The same is true in the management of for- est lands. To manage timber holdings most profitably we must consider all the products that could be produced on the land and the markets that would bring the highest return (6).* We must consider the quality of the wood needed by these markets as well as the quantity. The greatest possible volume of wood from a tract of timber is not always the most desirable, even for pulpwood. Quality and density are very important. Longer rotations with an end crop of sawlogs and veneer bolts and intermediate harvests of other crops appear to be the most effective management plan of the future. From such management 1/2 to % of the total wood grow,n would be available for some form of chem- ical utilization. Diversified utilization processes and plants must be devel- oped before intensive forest manage- ment is possible or profitable. ■Presented it meeting of the Forest -Bioducts Research Society, Florida -Georgia -Alabama Sec lion. Oct. }0. IflV it Radium Springs. Ga. 'Maintained at Madison. Wis., in cooperation with the University of Wisconsin. "Numbers In parentheses refer to literature cited at the end of this report. But first, wood utilization in general must be considered. There are two broad types of utilization — mechanical and chemical. Under mechanical utili- zation would be grouped such prod- ucts as lumber, veneer and pLywood, poles, piling, and fence posts. Under chemical utilization would be the whole range . of fiber products, from those made from coarse whole wood fibers to the most highly refined and purified chemical dissolving pulps. Also included would be products made by processes in which the chemical constitution of the wood rather than its size or shape is all important. Even in the mechanical uses of wood, chemistry plays a large role. Many new products are the result of combining paper, resin, and wood. Low-grade lumber, for example, can be covered with a resin-impregnated paper overlay to mask gaps, checks, and knots and to give a hjghly paint- able product. With specially designed papers the shrinking and swelling of lumber may be -partially controlled. For a long time I have felt that we have devoted too much time to inves- tigating the cutting and uses of high- grade clear veneers. We should spend more time cutting veneer from low- grade logs and finding ways of using the resulting material. One company has done just that and is producing a paper-covered veneer from a hardwood species that is so poor it has no other use (12). Another is using a softwood species — integrating the operation with a plywood plant (13). At least four companies are in production of a prod- uct of this type. Rsin Combinations Paper^Cbvered veneer is proving ex- tremely useful in such varied products as shipping containers and furniture. It seems to have one of the brightest futures of any recently developed prod- uct. Several types of resin-bonded pa- per honeycomb cores have been de- signed for use as core material for sandwich panels. In this type of con- struction most -of the stresses are taken by the facings; however, the core may be chosen for its insulating or sound- absorption value. The basic work was completed about 8 years ago. At pres- ent three companies are producing a resin-impregnated paper honeycomb core material. One combination of resin and wood that has reached the proportions of a new industry is laminating in which wood is glued together parallel to its grain. The performance and strength properties of laminated timbers are better than solid ones. Checking and splitting during seasoning may be eliminated. The lower moisture con- tent and the most efficient arrange- ment of growth characteristics of the wood permits higher strength values. The'parts of greatest stress — -the face laminations — may be of clear mate- rial with center lamina of lower grade knotty material. Not only are timbers laminated but also curved structural members. The most recent development has been the production of lamin/dcd di mension arid finish lumfc ter permits the upgradi: construction grades knots and other ing and end scat as stepping, and stylesj/^ N^ *0, SOroilization Ny jK mxtarjproblem confronting users C^ o^^'oaQ is the shrinkipg and swellineX N pf ^wood under afferent moisture^ condiftons. At the Laboratory we hAr worked Bar many years on the^dirna sional stabHjzation of wood and/have developed twWproduct* thutr j/k now in limited use-^VrnpA-g> an>r compreg (9, 10, 15). BotS^if- rhe^e are costly because a phenolicVesin is intorpo- raicd in the wood structure. With 30 percent resin the shrinking and swell- ing of wood can be reduced by about 60 percent. Reprinted from the Journal of the Forest Products Research Society, Vol. 4, No. 1. page 10 1954 P. O. Box 2010, University Station, Madison 5, Wis. Impreg, the resin-impregnated wood, is being manufactured by one company, not for its dimensional sta- bility but for its resistance to acids. Material for wood tanks to be used for storing acid is being impregnated with a phenolic resin. A small amount, of the material has been used in a number of other products. Two companies are manufacturing the resin-impregnated compressed wood, compreg. Most of it is being used for tooling jigs and forming dies. Its light weight compared to metals, relatively low cost, and ease of repair- ing make it highly desirable for these uses. One plant reported that its pro- duction was increased by as much as four times by the use of compreg dies instead of metal dies. If the resin con- tent is reduced to 5 to 10 percent, the toughness of the product is increased and its resistance to impact or shock is improved. Such material is more suit- able for shuttles and picker sticks in the textile industry than the higher lesin containing products. The Forest Products Laboratory is still working on improving the dimen- sional stability of wood. Much funda- mental work remains to be done be- fore a low-cost method will be de- veloped that will have universal application for such highly competi- tive products as doors, windows and drawers. Before leaving the subject of im- proved wood, we should consider the preservative treatment of wood, since that is one way of making an "im- proved" wood. As the result of more than 10 years of research, Dr. Roy Baechler of the Forest Products Labo- ratory has developed a new process for preserving wood called the double- diffusion process (1). Although the process was developed primarily for small-scale nonpressure treatment of fence posts, it shows considerable- promise for treating lumber. Green posts are placed upright in a barrel containing a copper sulfate solution, and the chemical diffuses into and up the posts. After about 2 days the posts are transferred to a barrel con- taining sodium chromate solution and permitted to soak for 2 days. The sec- ond chemical is taken into the wood structure and the two chemicals com- bine within the wood structure to form insoluble copper chromate, a compound toxic to insects and fungi. One hundred posts treated by this method have been in a test plot in Mississippi for more than 13 years. To date only one of this group has failed. Other chemicals and many spe- cies are under investigation. Chemical Utilization Now let us turn to the chemical utilization of wood. The raw material for chemical utilization should be ma- terial that has no value for structural purposes, that is, the residues from logging and manufacturing. It has been estimated that over 100 million tons of this material are produced each year in the United States (11). Residues can be classified as chip- pable — slabs, edgings, and trim — and nonchippable — shavings and sawdust. Chippable residues can be used for any form of chemical utilization, but the nonchippable residues are the problem children. At present they are suitable only for such low-grade uses as animal bedding, mulching, fuel and a few specialized uses such as floor sweeping compounds and fur cleaning preparations. At present the most profitable way to use wood residues is to convert them into chips and to process them into pulp. Both softwoods and hardwoods can be used. Each year more barkers (both whole log and slab barkers) and chippers are being used at saw- mills and veneer mills to produce pulp- able material. In the Pacific Northwest more than 100 chipping plants have been built at sawmills and plywood plants. The advent of the semichem- ical process now makes feasible the utilization of the cull hardwoods. An- other new process, prehydrolysis kraft, is being used to convert cull hard- woods into high-grade dissolving pulp, the rayon from which is superior for tire cord. However, in spite of the tre- mendous expansion in the pulp and paper industry, this cannot possibly be the complete answer to the problem of utilizing wood residues. Recent studies have shown that the residues of most species can be proc- essed into hardboard. Since 1948 the productive capacity for hardboard has doubled and still more plants are being planned (5). Much of this material goes to the industrial market where it is cut up and fabricated into other products. It is made from chips that have been fiberized, formed into mats, and pressed into flat sheets. Resin bind- ers are often used to strengthen the product. Particle Boards There is a whole new class of boards called particle boards that are also produced from the chippable por- tion of wood residues. The wood is usually defiberized in a hammer mill, resin is added, the moisture content is controlled, and the material is pressed into sheets. The Forest Products Labo- ratory is now evaluating the effect of particle size and shape on the proper- ties of such boards. Core material pro- duced by rhis method is competing satisfactorily with lumber core in a number of plants. It can be surfaced with paper, specially prepared flakes of wood, veneer, plywood, or even hardboards. Boards made from wood residues are one of the coming indus- trial materials. I believe we have seen only the beginning of the manufacture of this type of product. One of the most promising products is a board of medium density. A large unexplored field is the man- ufacture of a fiber that is suitable for producing molded products with either high or low resin content. These might vary all the way from toy parts and toilet seats to moldings and parts for kitchen cabinets. Experimentally, win- dow frames and sills have been pro- duced. Extrusion molding of shapes shows great promise. Now let us consider the problem children among wood residues — saw- dust and shavings. Wood hydrolysis is the most promising means of chemi- cally utilizing these materials because it is adaptable to all species and all forms of residue (7). This process al- lows us to separate wood into two ma- jor components — cellulose or its prod- ucts, and lignin. Theoretically, complete hydrolysis should produce about 1,300 pounds of sugar and 500 pounds of lignin per ton of dry wooa. Since some sugar is destroyed by the hydrolyzing chemi cals, the theoretical yield is never ob- tained. However, a percolation process now in use yields about 1,000 pounds of fermentable and nonfermentable sugar per ton of dry wood. The cellulose fraction of wood con- tains not only a material that is made up of a building block of glucose (corn sugar), but a material called hemicellulose that contains an appre- ciable amount of pentose sugars, mainly xylose. Xylose, which will run as high as 30 percent of the cellulose in hardwoods, appears to have a bright future as a raw material for the pro- duction of furfural. All of the readily available agricultural residues, such as corncobs, oat hulls, and rice hulls, now are being used to produce furfural, so any increase in production of this chemical must come from a new source. That new source appears to be hardwoods. Furfural is the final decomposition product of the pentose sugars during the acid hydrolysis of wood. The final decomposition product for the hexose sugars is levulinic acid. Both are valu- able intermediate organic chejnicals. Levulinic acid now sells for $5.00 a pound and is being used only in the pharmaceutical industry. Its future will be very bright indeed for synthetic fibers if it becomes available in the price range of furfural, that is, 9 cents a pound. Three companies now have pilot plants in operation for the production of furfural and levulinic acid. The Forest Products Laboratory has been doing fundamental research along these lines for a number of years. Wood-sugar molasses with a sugar concentration of 45 percent can be used for animal feeding (4). Feeding tests have shown that the sugar in wood molasses is equal to the sugar in blackstrap molasses in feed value. Wood sugars can be hydrogenated to sorbitol (a commercial humectant), ethylene and propylene glycols, glyc- erine and erythritol. A number of different yeasts can be grown on wood sugar. Depending on the type and the growing condi- tions, they may be high in fats, high in B vitamins, or as much as half pro- tein. One plant now is producing Torula yeast from the sugars in spent sulfite liquor, and another 2y 2 million dollar plant is under construction. The yeast is used as a high vitamin protein feed and as a source of pharmaceu- ticals. The original objective of hydrolyz- ing wood to sugars was to produce alcohol by fermentation. However, a number of other fermentation products can be obtained under properly con- trolled conditions. These include acetic, butyric, lactic, and citric acids, and acetone, butanol, butylene glycol, and glycerine. The use of wood sugar depends upon its production at a cost compar- able to the competing sugar whether it is blade strap molasses, invert sugar, or corn sugar. Much of the economics of any process of wood hydrolysis is dependent upon a profitable use for the lignin residue or upon a uniform constant supply of sugar at a fixed price. A number of uses have been found for lignin (3), but much more basic research is needed to establish its ex- act nature and to put it to best use. It differs from the other constituents of wood in that it is not converted to low-molecular-weight compounds when hydrolyzed with acids. It is a store- house of aromatic materials whose building block is phenyl propane. The lignin residue from the sulfite pulping process consists of lignosulfo- nates that can be converted into vanil- lin, the vanilla flavoring in your ice- cream, and such products as oil-well drilling compounds, tanning materials, and linoleum adhesives. These mate- rials do not use much of the available lignin, but the Sulfite Pulp Mill League of Wisconsin located at the In- stitute of Paper Chemistry and many other groups and pulp mills are doing utilization research that ultimately will provide a large-scale use for this prod- uct. One of the most obvious uses for lignin, since it is the binding material in wood, is as an adhesive or as a component of a plastic. However its flow properties must be improved. Ultimately, because of the great quan-. tities available, the best opportu- nities for the use of Jignin may be in chemical degradation and separation of the various products. Such processes as caustic treatment, pyrolysis, hydro- genolysis, and chlonnolysis or other oxidation processes are possibilities, but much basic research is needed. From the high lignin residue of the acid hydrolysis process it may be pos- sible to produce an activated char, per- haps by the fluidized bed technique worked out in the petroleum industry. The Georgia Institute of Technology made a valuable contribution to the study of wood carbonization by inves- tigating the fluidized bed principle for producing charcoal from sawdust (14) . While discussing carbonization, we should mention the opportunities in the domestic and recreational market for charcoal produced in small kilns- close to the market. Although this use of charcoal appears to be expanding, little has been done in the way of intensive marketing of a specialty product for the small consumer. It appears feasible that a small cinder block Connecticut type kiln might be integrated with intensive forest man- agement operations to convert logging residues into a cash product, especially in areas where low-cost labor is avail- able. The hardwoods are the preferred species. Extractives, another component of wood, form the basis of the large naval stores industry in this Southeast region. Such an industry can also be integrated into a management plan. The Forest Products Laboratory has done little work in this field in recent years be- cause of the intensity of work carried on by the Bureau of Agriculture and Industrial Chemistry. The Forest Serv- ice has concentrated on the forest man- agement phases. Now I would like to mention three fundamental chemical investiga- tions being carried on at the Madison Laboratory. In the first of these cellu- lose was treated with high-energy radiation to make a product that is essentially soluble in water (8). This is a drastic and costly treatment How- ever, a similar but milder treatment may be useful in increasing the re- action speed of cellulose in its con- version to plastics, rayon, and other products. This fundamental research project has produced some interesting and valuable information. Many of the new developments in wood utilization depend upon gluing Eleces of wood together, and yet we now very little, about this phenom- ena. New and better adhesives are developed largely by trial and error methods. The Laboratory now is un- dertaking, after a lapse of some 20 years, research on the fundamental mechanism of adhesion. The problem is being approached from three di- rections: (1) the forces of adhesion that bind the adhesive to wood. (2) the forces of cohesion that hold the adhesive together and resist its break- ing, and (3) the stress-strain rela- tionships within a glue film. This third part should provide information on the effect of additives on the prop- erties of an adhesive. The adhesion project is strictly basic research, but we hope the results will be useful in designing and formulat- ing adhesives to do specific jobs. For particle boards and laminated lum- ber, an extremely low-cost adhesive is needed. In fabricating airplanes, on the other hand, the cost of the adhe- sive is secondary to its performance. Tests have already shown that, pro- viding the surface is properly pre- pared, the cohesive forces are always weaker than the adhesive forces; the glued object does not break at the point of contact between the adhesive and the object, but rather in the glue film or in the material being glued. Another investigation that will be started shortly is on the fundamental mechanism of natural durability; that is, what is it that makes some woods durable while others decay rapidly? Previous work in this field was not aimed specifically at the fundamental mechanism, but rather at the relation of the molecular configuration includ- ing the side groups to toxicity. This work at the Forest Products Labora- tory by Bateman and Baechler (2) led to the development of tetrachloro- phenol and finally to pentachloro- phenol, which now is a recognized preservative. The reason for looking into natural durability now is the development of new techniques — the techniques of chromatography and infrared spectro- photometry. They should contribute much toward the solution of the problem. Basic information in the field of chemical utilization of wood is very short. If we are to continue to make- progress in this field, we must empha- size basic research right along with the fields of applied research and de- velopment. The development of any chemical process for utilizing wood, or any other material, is expensive. It requires time, money, and manpower. Even UNIVERSITY OF FLORIDA 3 1262 09216 2840 with unlimited funds and men it is a rare occasion where a process can be developed and a full-scale industrial plant built in less than 5 to 10 years. Chemical utilization of wood puts one into the chemical industry where capital costs are high and manpower requirements are low. The capital in ; vestment averages about $1.50 for every dollar of manufactured product. For example, if the output of a plant would be valued at a million dollars a year, the capital investment would be about l-Y 2 million dollars. To de- velop the chemical utilization of wood satisfactorily, it may be necessary for a number of primary manufacturers in the forest products industries to group themselves together as one ma- jor company that will purchase its raw materials from the wood residues of primary manufacturers and forest- land managers on a long-term basis. The Forest Products Industry must not expect the magic wand of research to turn her into a Cinderella. She must do her part by sprucing up and have enough gumption to go to the ball. References 1. Baechler, R. H. 1953. How to Treat Fence Posts by Double Dif- fusion. Forest Products Labora- tory Report No. R1955. 2. Bateman, E. and Baechler, R. H. 1937. Some Toxicity Data and Their Practical Significance. American Wood Preservers Asso- ciation Proceedings, vol. 33, p. 91. 3. Locke, E. G. and Johnson, K. G. Wood Resources for the Chemical Industry in the East Northcentral States, Ind. Eng. Chem., March 1954 (In process of publication). 4. Harris, E. E. -1950. Hydrolysis of Wood for Stock Feed. Fores : Products Laboratory Report No. R1731. 5. Lewis, Wayne C. 1952. The Hard- board Industry in the United States. Journal of the Forest Prod- ucts Research Society, vol. II, No. 4, p. 3. 6. Locke, E. G. 1949. Patterns for Integrated Complete Wood Utili- zation. The Timberman, vol. L (50), p. 44. 7. Saeman, J. F. 1952. Status of Chemical Utilization of Wood Waste. Journal of the Forest Products Research Society, vol. 2, No. 5, p. 50. (Dec. 1952). 8. , Millett, M A., and Lawton, E. J. 1952. The Effect of High-Energy Cathode Rays on Cellulose. Ind. Eng. Chem., vol. 44, p. 2848. 9. Stamm, A. J. and Seborg, R. M. 1951. "Forest Products Laboratory Resin-Treated, Laminated, Com- pressed Wood (Compreg). For- est Products Laboratory Report No. 1381, revised. 10. Stamm, A. J. and Seborg, R. M. 1950. Forest Products Laboratory Resin-Treated Wood (Impreg). Forest Products Laboratory Re- port No. 1380, revised. 11. Winters, R. K., Chidester, G. H., and Hall, J. A. 1947. Wood Waste in the United States. Re- appraisal of the Forest Situation, Report 4. Forest Service, U. S. Department of Agriculture. 12. Whiton, Arthur L. 1953. Crave- neer as Used in the Packaging Field. Journal of the Forest Prod- ucts Research Society, vol. Ill, No. 5, p. 103. (Dec. 1953). 13. Roberts, J. R. and Fisken, A M. 1953. Ply -Veneer Shipping Con- tainers, Journal of the Forest Products Research Society, vol. Ill, No. 5, p. 105. (Dec. 1953). 14. Morgan, L. W., Armstrong, G. M. Jr., and Lewis, H. C. 1953. Chem. Eng. Prog. 49, No. 2, p. 98, Feb. 1953 15. Locke, E. G. 1952. Modified Woods. Journal of the Forest Products Research Society, vol. 2, No. 4, p. 54. (Nov. 1952). Z M 966U5 F